A secure holographic system is proposed, based on the principle of two-wave encryption in the Fresnel domain under convergent random illumination. The convergent random wavefront, instead of the commonly used plane wavefront, improves the security of a holographic encryption system, providing better protection from unauthorized users. Our system has two new encryption parameters (the convergence distance and randomized lens phase function) in addition to the propagation distance and random phase masks in the reference arm. Validity and feasibility of the proposed method are verified with numerical simulation and experimental results.